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Earthquakes

Earthquakes. Chapter 22.5. Real- Time Earthquake Data. http://earthquake.usgs.gov/. EQs. EQ = Movement of E’s lithosphere that occurs when rocks in the lithosphere suddenly shift, releasing stored energy. EQs occur b/c stress forces of have exceeded the strength of rock.

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Earthquakes

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  1. Earthquakes Chapter 22.5

  2. Real- Time Earthquake Data http://earthquake.usgs.gov/

  3. EQs EQ= Movement of E’s lithosphere that occurs when rocks in the lithosphere suddenly shift, releasing stored energy. EQs occur b/c stress forces of have exceeded the strength of rock. Stress builds when rocks along 2 sides of a fault snag and lock (friction) as stress builds – so does POTENTIAL ENERGY IN ROCKS When rocks are strained beyond limit – they break & move. (Potential  Kinetic Energy in form of seismic waves)

  4. Stress & Strain on Rocks Stress – Force that squeezes rocks together, pulls them apart, pushes in diff. directions. Stress causes strain or deformation (change in shape or volume) of rock Stress Does not exceed rock strength Exceeds rock strength Folds Faults

  5. Stress Does not exceed rock strength Exceeds rock strength Faults = Breaks in rock layers & movement along breaks Folds = Bending rock layers Low Temp. & Pressure – Near Crust High Temps. & Pressure

  6. Folds Anticline = up facing fold Syncline = down ward facing fold

  7. Faults

  8. Types of Faults 1. Dip – SlipMotion up or down fault surface http://www.windows.ucar.edu/tour/link=/earth/geology/fault.html

  9. Types of Faults 2. Strike – slip Sliding – Horizontal Movement 3. Oblique – slipdip-slip & strike slip combined

  10. Plate Boundary: Convergent Interpretation of Tectonic History Divergent Transform Thrust/Reverse Normal Strike-Slip

  11. EQ Vibrations • EQ vibrations begin at a point called a FOCUS. • Vibrations travel from focus through the earth’s crust as waves. • Surface directly above the focus is called the epicenter. • These waves can be detected and measured on earth’s surface with a SEISMOGRAPH.

  12. SEISMOGRAPHS Instrument that measures & records EQ waves. Strength of EQ waves is referred to as MAGNITUDE. Wave Motion: http://sunshine.chpc.utah.edu/labs/seismic/index.htm?ASPIRE_Session=964f1ed30b7e49ceb81bd77f444d9230

  13. 3 Types of Seismic Waves 1. Primary Waves (P waves) 2. Secondary Waves (S waves) • Surface Waves Each wave originates from the FOCUS of the earthquake. Each wave travels in a different way, at different speeds, and causes different amounts of destruction.

  14. Seismic Waves = vibrations produced by energy released during EQ • P Waves: Primary Wave • Arrives 1st & Travels FASTER. • Compress & Expand like accordion (like sound waves) • Move through Solids & Liquids • Least destructive Virtual EQs http://www.sciencecourseware.org/VirtualEarthquake/VQuakeExecute.html Seismic Waveshttp://www.geo.mtu.edu/UPSeis/waves.html

  15. Seismic Waves S Waves – Secondary • What you FEEL in an EQ • Rock moves up & down or side to side (Snake-like) • Arrive after P • Move only through SOLIDS

  16. Seismic Waves: Surface Waves • Surface Waves develop when vibrations reach surface • Slowest waves • Most destructive, most damaging • More P & S wave animations:http://www-rohan.sdsu.edu/~rmellors/lab8/l8maineq.htm • Video clip:http://news.bbc.co.uk/1/hi/sci/tech/4126809.stm

  17. Rating Earthquakes Earthquakes are rated in terms of MAGNITUDE or INTENSITY by different scales. • Moment Magnitude Scale • Richter Scale • Mercalli Scale

  18. Moment Magnitude Scale • Uses a seismogram • Rates on scale from 1- 10 • Looks at Eqs in terms of ENERGY • Each # releases 31 times more ENERGY than the # before it. Example A 6 releases 31 times more energy than a 5, and a 5 releases 31 times more energy than a 4. The energy difference between a 4 and a 6 EQ is 31 X 31 = 961

  19. Richter Scale • Uses a seismogram • Rates on scale from 1- 10 • Looks at Eqs in terms of the SIZE OF THE WAVES • Each # has waves 10x bigger than previous # 1 – 3: Small earthquake waves – very little shaking 4 – 6: Moderate earthquakes – noticeable shaking and some damage 7 - 10+ BIG Earthquakes – Very destructive

  20. Mercali Intensity Scale • Measures observed RESULTS or DAMAGE of Earthquake on a 1 – 12 scale • Degree of shaking and DAMAGE to structures • Don’t need a seismogram • Link • http://www.abag.ca.gov/bayarea/eqmaps/doc/mmi.html

  21. EFFECTS OF EQs • Deaths & Injuries • Damage to buildings & structures • Underground water and gas pipes break – floods & fires • Landslides • Tsunamis

  22. Seismic Waves are used to Study Earth’s Interior P and S waves are “bent” and their velocities are affected as they move through material of varying density Link: http://sunshine.chpc.utah.edu/labs/seismic/index.htm?ASPIRE_Session=964f1ed30b7e49ceb81bd77f444d9230

  23. Latest Quakes http://earthquake.usgs.gov/eqcenter/recenteqsww/Quakes/quakes_all.php Top Ten Lists http://earthquake.usgs.gov/eqcenter/top10.php

  24. Links Virtual Earthquakes http://www.sciencecourseware.org/VirtualEarthquake/VQuakeExecute.html Wave Types http://www.geo.mtu.edu/UPSeis/waves.html Triangulation & “Hearing EQs” http://www.seismo.unr.edu/ftp/pub/louie/class/100/seismic-waves.html More virtual seismograms http://www-rohan.sdsu.edu/~rmellors/lab8/l8maineq.htm Earthquakes outline subducting slab – Interactive Web Lab http://openlearn.open.ac.uk/mod/resource/view.php?id=172185

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